You simply can't do that just by using a sleeping bag and what's more: the cover itself can be used as a convenience bag in survival situations, light camping and tropical regions.

Indeed, another important factor to consider before purchasing a sleeping bag is the span of temperatures that you expect to encounter while you use it. It is not the same to sleep in Colombia as in Scandinavia.

No piece of outdoor gear is suitable for all climates, and it would be of little use to purchase a top-quality sleeping bag if you can't use it due to the fact that it was not designed for the temperatures that you are facing at any particular moment.

The idea of providing yourself with three elements instead of one is to minimize this problem and to increase both your flexibility and the capability of your sleeping system on cold or damp areas. In other words, it makes it possible to sleep in situations whe it would be extremely uncomfortable otherwise.

Alas, you should also consider the kind of filling that you want to have in order to obtain a good sleeping bag. The filling is the key of the bag's functionality, and the best ones are duvet or geese feathers, and hollowfill, which is a synthetic product.

Duvet is somewhat better and more elastic than hollowfill, but it is also somewhat less resistant and durable. Sleeping bags made filled with duvet can be easily compacted for storage, but require some more care.

If it starts raining, you should cover your backpack andespecially your sleeping bag using your poncho.